The present invention relates to a surgery lamp of the type having at least one arm with a spring equalizer for counterbalancing the lamp head, a uniaxial joint associated with the arm, and electrical means for locking and unlocking the joint.
Such surgery lamps are suspended movably on an arm and must be held securely in the working position once they have been set, but it must also be easy to release and readjust them to a new working position. In the head of the surgery lamp a plurality of individual projectors are disposed so as to eliminate shadows in the operating field that is to be illuminated, while possibly due to additional accessories such as recording apparatus, focusing systems etc., the individual lamp head acquires a relatively great mass which varies according to the nature of the accessories and can lead also to a shift in the center of gravity. The result will be increases in the moment of inertia and in some cases imbalances with regard to adjustability. Large lamps have a plurality of individual projectors as light sources. They produce heat whose input into the operating field is prevented or reduced by devices such as cold-light mirrors, filters etc., thereby further increasing the mass of the lamp head. Nevertheless the lamp head must be suspended in the operating room to send light freely in any desired direction and must be easy to move. It must remain fixed in the set position immediately after it is adjusted, without drifting.
It is known to hang operating lamps from the ceiling on a vertical pivot which also conceals power lines. This pivot is joined by one or more substantially horizontal or inclined arms which are joined together by joints with vertical or tilted axes. The lamp head in practice is often situated in a forked free end of the last arm, all the arms forming the adjustable suspension, and can turn in the fork on an axis that is horizontal in the normal state.
An operating lamp with a plurality of projectors on a single mounting point is disclosed, for example, in German Patent 1,193,897.
A more or less great lateral distance from the mounting point is achieved by swinging the lamp about the vertical axes. The vertical distance from the mounting point is made adjustable by joints between the arms and having horizontal axes in the normal state.
With increasing lateral departure from the mounting point, the moment contributed by the mass of the lamp head acts around these horizontal axes and has to be counterbalanced.
It has already been proposed to solve the problem with rails attached to the ceiling of the operating room, on which a laterally running carriage is suspended, on which the lamp head is located with an additional linkage (cf. German Patents 863,528, 1,020,288, 1,058,447 or 1,102,673). In this design of the suspension of operating lamps additional problems are created by the fact that the operating table, as the field to be illuminated, has to be aligned with the rails. If the rail is mounted fixedly in the operating room, the freedom of movement of the operating lamp is then limited. Another serious problem arises from the fact that an exposed rail system above an operating field is a source of septic contamination which cannot be accepted in the sterile operating room.
In order to be able to retain the arm suspension well sealed off against this and nevertheless minimize the problems occurring in the case of great changes of position, it has been proposed to provide a plurality of mounting points on the ceiling (German Patent 927,864 or 1,156,363). These solutions minimize the problem of balancing, but limit the mobility and easy adjustability of an operating lamp. In practice, these solutions have not been widely accepted. The subject of the present invention, however, is addressed to surgery lamps which are suspended at a plurality of mounting points.
In practice, the problem here involved of balancing the weight has been dealt with by a proven balancing system using springs in the arms of the suspension. In the joints between the arms there is associated with each axis that is horizontal in the normal position a spring which extends in one of the adjacent arms, and it is joined by means of a lever to the attached arm so that the force of the spring counterbalances the connected weight (cf. German patents 1,097,928 and 1,810,552, which corresponds to U.S. Pat. No. 4,517,632 . This equalization of weights by springs cannot be a complete solution. The nonlinear spring characteristic and the increase of the moment of the weight with increasing distance from the mounting point cannot be completely matched to one another, inasmuch as the distance from the mounting point depends predominantly on the movement about the vertical axes of the suspension. Therefore a residual moment must be reckoned with, part of which cannot be compensated, and which must be otherwise taken up and held if a stable fixation of the lamp head is to be accomplished. On this it was proposed long ago (namely in German Patent 1,012,571) to prevent the tilting movement of the lamp head about a substantially horizontal joint by shifting the equalizing spring outwardly and combining it with a spindle drive to be operated by hand. Each adjustment then requires, however, that the spindle be rotated by hand. A rapid movement about the joint thus bypassed is not possible. But surgeons precisely require the possibility of quick correction of the incidence of the light in the course of an operation in order to be able to adapt the light to the situation of the moment. Any dentist's lamp must offer this possibility.
Motorized adjustments with self-locking motors in the arms of the suspension do permit the desired adjustment depending on small deflecting movements of a handle on the lamp head in the direction of the desired adjusting movement (German patent 1,797,040), but this motorized adjustment often has a still too long response time. The limited motor speed does not produce an immediate readjustment, and a corresponding overshoot control circuit has to be optimized so that when the end point of the movement is reached it will not be overshot and require readjustment. In practice, therefore, the free adjustment of a surgery lamp that can be performed directly by hand is preferred. To facilitate this method of adjustment it is proposed in German Patent Disclosure Document 32 43 700 (which corresponds to U.S. Pat. No. 4,517,632) to provide the joints for the mounting of the lamp body with a brake which can be operated via electromagnets when the surgeon or other person actuates a sensor on the lamp head. In practice, the wear on the frictionally interacting brake elements caused by the operation of the adjustment must be dealt with, and increasing wear of the brake elements even in a single joint can make the lamp no longer reliable in operation.